The invention relates to an over-center hinge for cabinet doors having a door jamb-related part which can be fastened to the door jamb of a piece of furniture, and a door-related part made in the form of a recess-mounting cup joined by a linkage to the jamb-related part. The cup has in its circumferential wall, adjacent its bottom, a cam or tongue mounted for pivoting under the bias of a compression spring toward the interior of the cup by a certain angular amount; this cam has a cam surface sloping upwardly from the cup bottom from the outside toward the inside, on which surface a rider means provided adjacent the linkage end of the jamb-related part rides during a portion of the opening and closing movement between the hinge-closed position and a dead center position and forces the door to the closed position; a stop means in the form of a swivel arm pivoted inside of the hinge cup at a distance from the pivot axis of the cam or tongue, with its free end pointing toward the cam and terminating in a stop edge parallel to the pivot axis is made for pivoting from a position in which the stop edge is below the cam surface of the cam to a position in which the stop edge holds the cam precisely in its dead-center position.
A hinge of this kind is known from German Offenlegungsschrift No. 30 18 184 corresponding to U.S. patent application Ser. No. 261,472, filed May 7, 1981, now Pat. No. 4,422,214, which combines the simple, proven design and reliable operation of over-center hinges having a resilient cam in the hinge cup with an over-center characteristic which formerly could be achieved only by considerably more complex and therefore more expensive embodiments. In the known hinge, the automatic movement of the swivel arm to the dead-center position when the hinge is opened is accomplished by a driving mechanism which snap-fastens the swivel arm to one of the links of the linkage mechanism so as to carry it over the necessary distance. In the dead-center position, the swivel arm runs against an abutment in the hinge cup. As the opening movement of the hinge continues, the part of the link mechanism that carries the swivel arm with it is therefore unsnapped from the swivel arm, so that the latter stops precisely in the position in which its stop edge holds the cam in the position associated with the dead-center position of the over-center mechanism. Experiments have shown that this snap-catching of the swivel arm during the opening of the hinge functions perfectly during a great number of operations. Nevertheless, it is, of course, quite impossible to prevent wear on the surfaces of the snap mechanism which produce the snap-catching action, so that ultimately the swivel arm will no longer function with the necessary reliability.
It is the object of the invention to improve the known hinge such that it can operate without the gripping or snap-catching mechanism that operates the swivel arm to hold the tongue or cam in the dead-center position when the hinge is opened.